It's best to work in concert with your doctor, and as a parent you'll of course need to exercise your best judgment. It is possible that the itching and hives are related to the Adderall. Sometimes it's prudent to discontinue the medication and observe the results. Let the feedback speak for itself.
I have to tell you from experience - my son developed itching and hives. He was about scratching his face raw. His doctor said to stop the medication immediately. He was afraid he would go into the "shock" that happens when someone is allergic to bee stings (I can't spell it!). I just thought you should know that my sons doctor said it CAN be a side effect. Be alert to his symptons.